1. Technical Field
The present invention relates to a dielectric composition, and a multilayered ceramic capacitor including the same as a dielectric layer.
2. Description of the Related Art
In general, electronic components using ceramic materials, such as a capacitor, an inductor, a piezoelectric element, a varistor, or a thermistor, or the like, include a ceramic element made of a ceramic material, internal electrodes formed in the ceramic element, and external electrodes mounted on a surface of the ceramic element so as to be connected to the internal electrodes, and refer to a multilayered ceramic electronic component using a thick film ceramic multilayered technology. Among the chip components, the multilayered ceramic capacitor has been widely used as components for a mobile communications device such as computers, personal digital assistants (PDAs), mobile phones, or the like, due to advantages such as a small size, high capacitance, easiness of mounting, or the like.
The multilayered ceramic capacitor is generally manufactured by multilayering a paste for an internal electrode layer and a paste for a dielectric layer by a sheet method, a printing method, and the like, and performing a co-firing process. However, at the time of performing the firing process under a reduction atmosphere, a dielectric material used in the existing multilayered ceramic capacitor, or the like, is reduced to be a semiconductor.
Therefore, precious metals such as Pd, and the like, which are not molten at a temperature at which the dielectric material is sintered, and are not oxidized even though the firing process is performed under a high oxygen partial pressure not allowing the dielectric material to be a semiconductor have been used as a material of the internal electrode.
However, since the precious metals such as Pd, and the like, are expensive, the multilayered ceramic capacitor made of the precious metals has difficulty in reducing the price. Therefore, as the material for the internal electrode, non-metals such as nickel (Ni), a nickel alloy, and the like, that are relatively cheap have been mainly used.
In addition, in the case in which the non-metal is used as a conductive material of the internal electrode layer, when the firing process is performed in the atmosphere, the internal electrode layer is oxidized, such that the co-firing process of the dielectric layer and the internal electrode layer should be performed under the reduction atmosphere.
In general, in the case in which the firing process is performed under the reduction atmosphere, the dielectric layer is reduced, such that an insulation resistance (IR) is decreased. Therefore, a non-reductive dielectric material has been suggested, and a dielectric magnetic composition for temperature compensation having a small change in temperature of electrostatic capacitance, and arbitrarily controllable at a range of −150 to +150 ppm/° C. has been increasingly demanded.
(Ca,Sr) (Ti,Zr)O3 composition has been mostly and widely used as the dielectric composition for temperature compensation in the related art. Referring to FIG. 1 showing a change in a temperature coefficient of capacitance and the following Table 1 showing a method showing properties according to the temperature coefficient of capacitance, a solid solution having stable temperature coefficient regardless of COG type temperature may be formed, and a dielectric constant and the temperature coefficient of capacitance may be changed depending on a composition ratio of Ca2+ and Sr2+ ions and Ti4+ and Zr4+ ions.
TABLE 1Temperature coeff.Toleranceppm/° C.Sym.ExponentSym.ppm/° C.Sym.0.0C−10±30G1.0M−101±60H1.5P−1002±120J2.2R−10003±250K3.3S−100004±500L4.7T+15±1000M7.5U+106±2500N+1007+10008+100009
It is generally well known that when Ca2+ and Zr4+ are added more than Sr2+ and Ti4+, the dielectric constant is decreased and the temperature coefficient is stable, but in contrast, when Sr2+ and Ti4+ are added more than Ca2+ and Zr4+, the dielectric constant is increased while the temperature coefficient is rapidly changed.
More specifically, the dielectric constant and the temperature coefficient of capacitance in the composition has a dielectric constant of 30 to 340 and a temperature coefficient of capacitance of 0˜−3400 ppm/° C. depending on ratio of Ca/Sr and Zr/Ti, and as the temperature coefficient of capacitance becomes stabilized, the dielectric constant is small, less than 50.